my check engine light came on yesterday so i went to autozone to use the OBD II diagnostic computer and it came back with "engine coolant temp." they told me its the heat sensor and that it either needs to be replaced or could be loose. this happened once also about 7 months ago so i took it to an acura dealer since i wasnt by my mechanic, and they just reset it and said it was probably a dummy light. should i bring it in to my mechanic or is there a way i could resolve the issue on my own.

for reference OBD II codes were:
PO118
Engine Coolant Temp
Circ: High Input

thanks!

 

oh and also the car idles awkwardly because of this: flip flops from a high (1.5 even after car has been running) to low idle (.7ish) as opposed to the .9-1 normal